Worksites, for example, mine sites, landfills, quarries, construction sites, etc., commonly undergo geographic alteration by machines performing various tasks thereon. For example, at a coal mining site, mounds of coal are continually moved by dozers about the site, onto conveyors, into chutes, etc., to prepare the coal for transport. Likewise, at an excavation site, terrain is altered by digging, grading, leveling, or otherwise preparing the terrain for various uses. During the performance of these tasks, the machines can operate in situations that are hazardous to an operator, under extreme environmental conditions, or at work locations remote from civilization. Accordingly, autonomous or semiautonomous machines are often utilized.
Autonomous and semiautonomous machines may be in communication with a general site controller located at a base station, and the machines may receive assigned tasks from the general site controller. The assigned tasks may depend on the location of the base station. As such, to ensure the safety of these machines, the site controller must accurately know the location of the base station.
An exemplary system that provides position monitoring is disclosed in U.S. Pat. No. 7,831,362 issued to Ishibashi et al. on Nov. 9, 2010 (“the '362 patent”). Specifically, the '362 patent discloses a machine equipped with a UPS system for measuring the location of the machine's body. Sometimes, however, the UPS measurement of the machine body's location is inaccurate. As such, the '362 patent also discloses a reference station that may correct inaccurate GPS measurements using various angle sensors, an inclination sensor, and a gyroscope located on the machine.
Although the '362 patent may account for inaccuracies in a GPS measurement of a machine, it does not address possible inaccuracies in the location of a reference station. The system also requires multiple sensors on each machine, which may be bulky and expensive. Lastly, the sensors may malfunction under harsh worksite conditions and render the '362 system unable to correct location inaccuracies.
The disclosed position control system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.